1. Field of the Invention
The present invention relates to liquid crystal display devices. More particularly, the present invention relates to liquid crystal display devices capable of black and white and color displaying.
The present invention also relates to a film with areas of differing optical retardation. More particularly, the present invention relates to such a film having a pattern of such areas of differing optical retardation.
Furthermore, the present invention relates to a new use of polydiacetylene. Yet more specifically, the present invention relates to a new use of polydiacetylene film.
2. Description of Related Art
A conventional liquid crystal display device having a time-sharing drive characteristic has a low transmission rate. Therefore, with so-called reflection type liquid crystal display devices, a color display was difficult. A reflection type liquid crystal display device is described in Japanese Patent Application Laid-Open No. 60-252325 (1985).
Linearly polarized light going through a conventional liquid crystal cell, e.g. a liquid crystal cell with twisted nematic liquid crystal material, was not only changed in its polarization direction, but had an elliptical distribution of the electrical vector as well. The changes to the line only polarized light in interference coloring of the light composed of the linearly polarized light and of the elliptically polarized light. To solve this problem U.S. Pat. No. 4,443,065 proposes to use, outside of the liquid crystal cell having control electrodes, a second liquid crystal layer with twisted nematic liquid crystal, such that the twist direction of the two liquid crystal layers are arranged in opposite directs. The retardation d*.DELTA.n is the same for each of the two layers. The longitudinal axis of liquid crystal molecules in the two liquid crystal layers are at 90.degree. to each other.
In U.S. Pat. No. 4,844,569 a similar device is described. In this patent, an optically anisotropic layer with opposite twist sense for the rotation of the polarized light between the liquid crystal cell and the polarizer is described. Among the optically anisotropic materials available, U.S. Pat. No. 4,844,569 describes stretched film of polyvinylalcohol. This patent also describes the use of two optically anisotropic layers, one on each side of the liquid crystal cell.